DTS and DD sound !!

hi guys! i have a problem that i don't understand. so i have a digital receiver z5500, sound card creative x-fi platinum series(receiver and sound card, digital connection through optic), and using kmplayer to spdif passthrough and let the receiver do the decoding.
on xp with sp3, i'm playing a DTS track which has 48khz sampling rate and 1509 kb bitstream and on the console of the receiver it says "dts digital" and it sounds awesome, no problem here, but when i'm trying to play another dts track with 48khz and 1411 kb bitstream it doesn't work, no sound comes out and on the console says "no digital data".

Is it possible that the built-in decoder of the receiver doesn't know how to decode??(just an idea)